Luby, Czech Republic, which was hit by a 3.6 mag tremor on Saturday. Image Zipacna1

Towns and villages across the western Czech Republic were shaken overnight by two separate earthquakes, the latest in a series of tremors to hit the region.

The Geophysical Institute, Academy of Sciences of the Czech Republic says it has recorded 10,000 earthquakes during the last 10 days in Nový Kostel area of the Cheb District, a region located close to the Czech Republic’s western border with Germany.

The earthquake swarm started on Tuesday 23 August and continued Saturday 03 September. While many have gone unnoticed by the local population some of the larger tremors, including more than two dozen quakes exceeding 3 magnitude have been felt in the towns of Chemnitz, Karlovy Vary, Birch, Bukovany and Luby.

The most recent, significant earthquake measured 3.7 magnitude and struck at 02:25 AM on Saturday. The shallow earthquake was measured at a depth of just 5 kilometres. According to the European-Mediterranean Seismological Center, the epicentre was located 1 km NE Bukovany (pop 1,798), 2 km SW Sokolov (pop 24,847), and 72 km NW Plzen (pop 163,953).

The quake occurred just over two hours after a quake measuring 3.6 magnitude on the Richter Scale hit. The epicentre was located less than 2 kilometres north of Luby, a two with a population of just over 2,500. The tremor was also felt 71 kilometres away in Gera, a city of some of 105,000 people.

In recent years, scientists have noted an increase in the movement of magma towards the earth’s surface in the Cheb Basin, western Czech Republic. They say rising magma could be one of the causes of the earthquake swarms, which regularly occur in the Vogtland, North-West Bohemia, the Fichtelgebirge and the Upper Palatinate. The last earthquake swarm to occur before this week’s activity was in 2008.

Commenting on the earthquake swarm, the Geophysical Institute, Academy of Sciences of the Czech Republic stated: “The activity started in the evening of 23 August and is almost continuous till now. Almost 10 000 events were recorded in total up to now. Already eight events M>3.0 and 200 M>2.0 occurred. The location of hypocenters directly below the NKC station, so it appears a new patch of the fault plane is being activated”.

Earthquake swarms are events where a local area experiences sequences of many earthquakes striking in a relatively short period of time. The length of time used to define the swarm itself varies, but the United States Geological Survey points out that an event may be on the order of days, weeks, or months. They are differentiated from earthquakes succeeded by a series of aftershocks by the observation that no single earthquake in the sequence is obviously the main shock. Earthquake swarms are one of the events typically preceding eruptions of volcanoes.